(1) Field of the Invention
The present invention relates to an apparatus and method for generating a bit-mapped pattern of a print character by embedding embedding-patterns on and inside the outlines of the bit-mapped character.
(2) Description of the Related Art
A method for securing the contents of stored documents against falsification or forgery, which has recently become a serious issue, has been developed.
One way of falsifying a document is to paste up a tempered document generated with the use of a document generation apparatus over a part of a stored document, without leaving any evidence behind. This way, for example, allows an amount of money printed on paper to be illegally rewritten, leaving a seal or signature as it is. As a result, it gets harder to reveal the presence of falsification.
In order to discover the falsification without fail, it is possible to embed data in every character contained in a document in order to indicate the originality of the document.
One example of such a code-embedded character technique is disclosed in the Japanese Laid-open Patent Application No. 56-36770. The art of the application is explained as follows with reference to FIG. 1.
First of all, data to be read are transferred into binary data, and each bit of the binary data is made to correspond to a coordinate of a print character in the horizontal direction. For example, when data to be read consists of 64 bits (8 bytes) and the bit-mapped character has 64.times.64 dots, then the 0th bit and the 48th bit of the data are made to correspond to the 0th dot and the 48th dot respectively. After this corresponding operation, the dots in the data corresponding to "1" are not filled in. If the 11th, 31st, and 51st bits are "1", the 11th, 31st, and 51st dots in the vertical direction are not filled in. Thus, binary data expressed in blanks can be read through raster scanning.
If these data are used to certify the originality of every character in a document, the presence of falsification can be detected without fail.
Adding the document generator's name and the date of the generation to the data to be read makes the guarantee more firm.
The row and column of every character in a document can be checked by using the data to be read as the position of each character.
According to this conventional technique, the presence of falsification can be detected without fail as long as the data are firmly embedded in every character; however, the embedding is unreliable because of the frequent occurrence of bit garbling.
The width of pattern-embedded area is different depending on characters as apparent from the widths c10, c11, and c12 shown in FIG. 2, so that the width of margins at both sides of each character is also different depending on characters, as apparent from the margins b31, b32, and b33. Since the margins look the same as the blanked dots, the horizontal coordinates corresponding to the margins b31, b32, and b33 are mistaken as "1". As a result, data to be read tend to be garbled.
Although it is possible to make the width of pattern-embedded area uniform, it spoils the appearance of the characters to be printed.